Account collision for offsetting player position

src/main/java/gay/ampflower/polysit/CollisionUtil.java

@@ -0,0 +1,114 @@
+/* Copyright 2024 Ampflower
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+package gay.ampflower.polysit;
+
+import com.mojang.logging.LogUtils;
+import net.minecraft.entity.Entity;
+import net.minecraft.entity.EntityDimensions;
+import net.minecraft.entity.EntityPose;
+import net.minecraft.util.math.Box;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+
+/**
+ * Checks the collision of the player in question
+ *
+ * @author Ampflower
+ * @since 0.6.0
+ **/
+public final class CollisionUtil {
+	private static final Logger logger = LogUtils.getLogger();
+
+	public static FittingPosition adjustFit(final Entity entity, double x, double y, double z) {
+		// The entity in question shouldn't be able to be placed beyond their jump
+		// height.
+		double max = y + JumpHeightUtil.maxJumpHeight(entity);
+		double maxFit = Double.POSITIVE_INFINITY;
+		double min = y;
+
+		logger.debug("{} => [{}, {}] @ ({}, {}, {})", entity, min, max, x, y, z);
+
+		Box box = getSmallestPose(entity, x, y, z);
+		final var collisions = entity.getWorld().getBlockCollisions(entity, box);
+
+		for (final var collision : collisions) {
+			for (final var bound : collision.getBoundingBoxes()) {
+				if (!bound.intersects(box)) {
+					logger.debug("Skipping box {} as unimportant to {}'s position", bound, entity);
+					continue;
+				}
+				if (bound.minY > box.minY && bound.maxY > box.maxY) {
+					maxFit = Math.min(maxFit, bound.minY);
+					// TODO: Verify that this would work in most cases.
+					// It does seem to in limited testing.
+					logger.debug("Skipping box {} as above {} for {}", bound, box, entity);
+					continue;
+				}
+				if (bound.maxY > min && bound.maxY < max) {
+					box = box.offset(0, bound.maxY - min, 0);
+					min = bound.maxY;
+				}
+			}
+		}
+
+		return new FittingPosition(min, getLargestFittingPose(entity, maxFit - min));
+	}
+
+	public static Box getSmallestPose(Entity entity, double x, double y, double z) {
+		final var standing = entity.getDimensions(entity.getPose());
+		final var sneaking = entity.getDimensions(EntityPose.CROUCHING);
+		final var swimming = entity.getDimensions(EntityPose.SWIMMING);
+
+		return smallest(standing, sneaking, swimming).getBoxAt(x, y, z);
+	}
+
+	public static EntityPose getLargestFittingPose(Entity entity, double y) {
+		return largest(entity, y, entity.getPose(), EntityPose.STANDING, EntityPose.CROUCHING, EntityPose.SWIMMING);
+	}
+
+	@NotNull
+	public static EntityDimensions smallest(EntityDimensions... dimensions) {
+		if (dimensions.length == 0) {
+			throw new IllegalArgumentException("length == 0");
+		}
+
+		EntityDimensions min = dimensions[0];
+
+		for (int i = 1; i < dimensions.length; i++) {
+			final var comparison = dimensions[i];
+			if (comparison.height < min.height && comparison.width < min.width) {
+				min = comparison;
+			}
+		}
+
+		return min;
+	}
+
+	@Nullable
+	private static EntityPose largest(final Entity entity, final double maxHeight, EntityPose... poses) {
+		if (poses.length == 0) {
+			throw new IllegalArgumentException("poses.length == 0");
+		}
+
+		double height = 0;
+		EntityPose fittingPose = null;
+
+		for (final var pose : poses) {
+			final var poseHeight = entity.getDimensions(pose).height;
+			if (poseHeight < maxHeight && poseHeight > height) {
+				height = poseHeight;
+				fittingPose = pose;
+			}
+		}
+
+		return fittingPose;
+	}
+
+	public record FittingPosition(double y, EntityPose pose) {
+	}
+}

src/main/java/gay/ampflower/polysit/mixin/MixinLivingEntity.java

@@ -6,12 +6,10 @@
 
 package gay.ampflower.polysit.mixin;// Created 2022-08-05T23:31:06
 
-import gay.ampflower.polysit.Main;
-import net.minecraft.block.ShapeContext;
+import gay.ampflower.polysit.CollisionUtil;
 import net.minecraft.entity.Entity;
 import net.minecraft.entity.EntityType;
 import net.minecraft.entity.LivingEntity;
-import net.minecraft.util.math.Direction;
 import net.minecraft.world.World;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
@@ -32,13 +30,10 @@ public MixinLivingEntity(EntityType<?> type, World world) {
 
 	@ModifyArg(method = "onDismounted", at = @At(value = "INVOKE", target = "Lnet/minecraft/util/math/Vec3d;<init>(DDD)V"), index = 1)
 	private double modifyY(double x, double y, double z) {
-		var pos = Main.blockPosOfFloored(x, y, z);
-		var block = this.getWorld().getBlockState(pos);
-		if (block.isAir()) {
-			return y;
+		final var fit = CollisionUtil.adjustFit(this, x, y, z);
+		if (fit.pose() != null) {
+			this.setPose(fit.pose());
 		}
-		var col = pos.getY()
-				+ block.getCollisionShape(this.getWorld(), pos, ShapeContext.of(this)).getMax(Direction.Axis.Y);
-		return Math.max(y, col);
+		return fit.y();
 	}
 }